Carburetor



Aug. 9, 1949 w. H. WEBER CAHBURETOR 3 Sheets-Sheet 2 Filed Oct. 6, 1944 INVENTOR.

K- M ATTORNEY FIG.3

FIG. 4

Patented Aug. 9, 1949 UNITED CIiRBURETOR Walter H. Weber, Detroit, Mich, assignor to Detroit Lubricatcr Company, Detroit, Mich., a

corporation of Michigan Application October 6, 1944, Serial No. 557,405

7 Claims. (Cl. 26i-10) ihis invention relates to new-.and useful improvements in carburetors for supplying combustible mixtures to internal combustion engines.

One object of the invention is to'provide a carburetor of the downdraft type having its parts compactly arranged and which is of simple construction such that it is capable of rapid and easy manufacture.

Another object is to provide a carburetor having means for cooling the fuel to be supplied to the mixing chamber.

Another object is to regulate the fuel-air ratio of the combustible mixture in accordance with the demands on the engine supplied by the carburetor.

Another object is to provide means to reduce the formation of gas bubbles in the fuel conduits,

thereby assuring proper fuel flow.v

'Another object is to provide a valve for controlling air admission to the carburetor mixing chamber and which is both manually adjustable and automatically operable by engine suction.

The invention consists in the novel construction and cooperative relation of parts to be more fully described hereinafter and the novelty of which'will be particularly pointed out and distinctly claimed. I

In the accompanying drawings to be taken as a part of this specification, there is fully and clearly illustrated a preferred embodiment of the invention, in which drawings:

Figure 1 is a top plan view of a carburetor constructed in accordance with the invention;

Fig. 2 is a view of the carburetor in front elevation;

Fig. 3 is-a view in elevation looking from the left 2;

Fig. "4 is a view in vertical central section on the line 4-.4 of Fig. 1:

Fig. 5 is a view of part of the carburetor in vertical section and taken on the line 55 of Fig. 1;

Fig. 6 is also a partial view in vertical section and taken on the line 68 of Fig. 1;

Fig. 7 is a detail view in vertical section on the line 1-1 of Fig. 5;

Fig. 8 is a bottom plan view of part of the carburetor, and

Fig. 9 is a diagrammatic view showing the interrelation of certain of the parts of the carburetor.

, similar air inlet throat ring 1.

Referring to the drawings by characters of reference, i designates generally the metal casing of the carburetor including a lower throttle body member 2 having an air inlet member 3 superposed thereon and secured thereto, the members preferably being die cast. The body member 2 has a pair of laterally positioned vertical cylindri cal bores or passageways 4, 5 therethrough providing downdraft mixing chambers. The mixing chamber 4 has, at its upper end, an air inlet 6 in which there is positioned a threat ring I for restricting and accelerating air flow from the inlet member 3 into the mixing chamber 4. The'ring i fills and is supported in a counterbore or annular recess in the upper end of the body member 2, such that the top face of the ring is flush with the top face of the body member. The bore or edge of the opening through the ring 'I is preferably of rounded downward diverging form or contour. The mixing chamber 5 is provided with a Extending horizontally from the side of the body member 2 and separated from the mixing chambers l, 5 by a vertical wall 8, there is a constant level fuel reservoir or float chamber 9 which is of substantially equal height with the passageways l, 5. The bottom float chamber wall I 0 lies within the height of the horizontal hollow clamping flange ll which-ex tends laterally from and in surrounding relation to the mixing chambers at the bottom end of the body member 2. The flange H has its top face formed by a horizontal web portion [2 from which a downward extending marginal rim i3 projects which is adapted to seat on and be clamped to the engine inlet manifold. Cooperating with the rim l3 there are tubular members or sleeves l4 forming the lower end portions of the pasageways l, 5 and which have their lower ends terminating in outturned flanges to seat against the manifold. These sleeves H are preferably of metal having a high resistance to heat transfer and are prefer ably of stainless steel. The bolt receiving apertures in the flange l I are formed by stainless steel tubes l5 outwardly flanged at their bottom ends to seat on the manifold. The hollow flange H has air inlet openings it through the rim l3 and has air outlet apertures H in the web portion l2, see Fig. 8. so that convection air currents can circulate through the interior of the flange Ii and around the lower ends of the passageways 4, 5.

Extending upwardly into the wall through downward extending bottom bosses within the fiange ll there are tubular cylindrical chambers l8, is which have their lower ends internally screw-threaded and which have their upper portions providing sub-atmospheric fuel wells. Screw-threaded into and closing the lower ends of the chambers I 8, Is there are main fuel jet plugs 20, each having an annular circumferential recess communicating with their respective fuel supply conduits 2|, 22 of uniform unrestricted bore and inclined downward from the interior of the float chamber 9. The plugs have calibrated main fuel jets or orifices 23, 24 communicating respectively with the conduits 2|, 22 and opening laterally into the lower ends of fuel conduit portions opening upwardly through the upper ends of the plugs 20. This construction exposes the plugs containing the main fuel jets to the cooling action of the convection currents which circulate through the flange II. The upper ends of the plugs 20 are provided with central tubular projections which extend, with a slip fit, into the lower ends of fuel tubes 25 which extend upward concentrically within the chambers l8, I9 to form the annular fuel wells. The upper ends of the tubes or members 25 extend and fit into cylindrical recesses in the upper end walls of the chambers l8, l9 and are sealed therein by the compressive force of the plugs 20, a sealing washer 26 being interposed between each of the plugs 20 and tubes 25 so that the lower ends of the fuel wells and also the joints between the plugs 20 and members 25v are efiectively sealed. The bores of the tubes 25 provide fuel conduit portions which communicate with the fuel wells l3, l9 through upper and lower cross apertures or air vents 21, 28 respectively. The bores of the tubes 25 register with upper conduit portions in the wall 8, which conduit portions intersect downward inclined bores 29 opening into the passageways 4, 5 respectively adjacent and below the throat rings 1. Tightly fitted in the bores 29 there are fuel nozzles 30, 3| discharging and projecting respectively into the passageways 4, 5. The nozzles 30, 3| are of Venturi form and extend into the passageways 4, 5 a distance substantially equal to one quarter of the passageway diameter. Each nozzle has an external surrounding channel registering with the vertical fuel conduit leading upward from its well. Each of the nozzles also has a plurality of radial fuel orifices 32 opening from its external channel into its Venturi throat. The nozzle receiving bores 29 extend through the wall 8 and are closed at their float chamber ends by disc plugs 33. The nozzles 30, 36 terminate at their inner ends short of the plugs 33 so that the inner ends of the bores 29 provide air chambers communicating with and feeding the nozzles 30, 3 I. Air is supplied to these bore chambers by a pair of passageways 34 which open upward through the top face of the throttle body member 2. The passageways 34 communicate with air supply ducts 35 which extend upward in the wall of and open into the interior of the hollow air inlet member 3. Air supply passageway or ducts 36 in the wall 8 and opening upward through the top face of the body member 2 serve to feed air to the upper ends of the fuel wells I8, is around the tubes 25 and above the cross vents 21. The air inlet member 3 has a horizontal bottom wall 31 through which there are calibrated air bleeds 3B registering one with each of the passageways 36- and controlling the sub-atmospheric pressure over the fuel in the wells l8, It. The mixing chamber passageways 4, 5 are separated by a vertical wall 39, see Fig. 4, which intersects the wall 8. The body member 2 has aligned external throttle shaft bearing bosses 40. 4| which receive a throttle shaft 42 journaled in an aperture through the wall 39. Fixed on or to the shaft 42 in the passageways 4, 5 there are throttle valves 43, 44 respectively which are positioned with their leading sides closely underlying the nozzles 30, 3| respectively and such that the nozzle bores are aimed and discharge substantially at the mid portions of the valves.

Extending across the passageways 4, 5 there are bridging conduit members or tubes 45, 46 respectively which are transverse to the throttle shaft 42 and communicate with the wells l8, l9 substantially in alignment with the air vents 28. The tube 45 discharges into the lower end of a vertical fuel conduit 41 extending upward through a vertical boss on the side wall of the member 2 and substantially opposite the well [8. The upper end of the conduit 41 discharges through a calibrated orifice 48 into a mixing chamber 49 which is supplied with air through a calibrated air bleed 50 through the air inlet bottom wall 31. From the chamber 49 there is a downward extending conduit 5| diametrically opposite the discharge end of the nozzle 30 and which terminates in an idling fuel jet or port 52 opening into the chamber 4 below and spaced from the trailing edge of the valve 43. The port 52 is controlled byan adjustable needle valve 53 having its stem projecting externally from the member 2. The conduit 5! is also connected to the passageway 4 by a port 54 inclined toward the inlet 6 and opening into the passageway 4 above the closed position of the trailing edge of the throttle valve 43 so that the port 54 serves to bleed air into the idling conduit 5| for closed and slightly open positions of the throttle valve. As the throttle valve is opened. the port 54 will change over from an air bleed and will serve as a fuel port and discharge fuel from the idling conduit 5| into the passageway 4. The idling conduit formed by passageways 41 and 5| provides an inverted U-shaped passageway which permits tilting of the carburetor to an angle of about 35 without flow of fuel through the jet 48 and thence into the mixing chamber. The positioning of the jets 32 in the main nozzles 30, 3| closely adjacent to the fioat chamber also permits this tilting of the carburetor without flow of fuel through the nozzles into the mixing chambers. The idling fuel conduits and ports which supply the passageway 5 are identical with those which supply the passageway 4 and therefore a detail description is unnecessary, the primes of the reference characters designating like parts.

The projecting throttle shaft end 55, see Fig. 2, has fixed thereon an operating lever 55 for connection to a remote control point such as the usual accelerator pedal. Journaled on the shaft end 55 between the lever 55 and the boss 40 there is a throttle adjusting lever 51 extending upward with its free end terminating in a laterally ofl'set cam follower portion or flange 58. The levers 56 and 51 are interconnected for movement in unison by a right angle pin 53 extending from the lever 55 and having its free end journaled in the swivelled end portion of an adjustment screw Bil which is adjustably screw threaded through parallel ears or flanges iii, of which one only is shown, and turned or bent backward from the side edges of the lever 51, see Fig. 3. This screw 50 provides for adjustment of the lever 51 relative to the throttle plates or valves 88, 88, Surrounding the bearing boss 48 there is a coil spring 82 having one end terminating in an eyelet to receive the screw 58 and having its other end secured, as at 68, in an aperture boss on the body member 2 such that the spring urges the throttle valves toward closed position and the lever 81 from right to left facing Fig. 2. The other end of the throttle shaft which projects from the boss 8| has an operating lever 58 journaled thereon which cooperates with an arm 85 fixed on the throttle shaft such that the lever 88 limits closing movement of the throttle valves while permitting the throttle shaft to have unimpeded valve opening rotation.

The cam follower flange 58 cooperates with and is urged by the spring 52 against a cam 88 forming part of a choke lever 51 iournaled on a projecting end portion of the air inlet choke valve shaft 88. The lever 81. is coupled to the shaft 88 by a lever 69 having a stop arm or finger 18 extending between spaced abutments formed by the radial side edges of an edge slot H in the lever 81. The lever arm 18- is urged in an air valve closing direction and against the corresponding slot end 'by a coil spring12 having one end secured, as at 18, to the lever 51 and having its other end secured, as at 14, to the arm 18. The stop arm 18 is cooperable with an abutment member 15 projecting from the inlet member 8 and serves to limit movement of the shaft 88 beyond full open air valve position. Secured on the shaft 68 within the inlet member 8 and controlling air flow therethroughto the passageway inlets 6, there is a choke valve 16 of the eccentric butterfly type having a high vacuum relief valve formed by air inlet ports 11 (of. which but one is shown) closed by a spring loaded valve disc 18 which is movable to open position against the force of the spring 18 upon engine operation under its own power, as is well understood in the art. The air valve 16 is limited to full open position by an abutment 88 on the inlet member wall 81.

Positioned at the intersection of the wells 8 and 89 there is a vertical cylindrical pump chamber 8| having a check valve controlled fuel inlet 82 in its bottom wall. The fuel duct forming the inlet 82 has its lower portion within a boss 88 positioned within the hollow flange II so that it is air cooled. This duct is fed through a downward inclined passageway or port 84 leading from the float chamber 8 so that tendency of air or gas 81 between the passageways 8 and 5. The nozzle 88 has discharge ports 88 directed laterally or horizontally across the air inlets 8 of the passageways I and 5. Flow of fuel by engine suction through the pump discharge duct 85 is prevented by a check valve 88 which is of elongated pencil form to reduce the flow area of the passageway 85, thereby cutting down the quantity of fuel which will trap above or on the outlet side of the valve seat. Within the chamber 8| there is a piston or plunger 8| having a piston rod 82 universally supported therein and abutting a compression spring 83 which, on the piston discharge stroke, is compressed by the rod 82 so as to provide lost motion and a follow up fuel discharge after the discharge movement of the rod 82 is-stopped. The piston 8| is provided with packing 88, preferably of leather, which is expanded outward against the wall of the chamber 8| by an annular resilient ring 85, preferably a helical coil spring of circular form and held in a circumferential recess in the piston 8|.

In the bottom wall of the pump chamber 8| there is a power jet 88 controlled by a valve member 81 having a stem projecting through the jet port and upward into the chamber 8| for engagement by the bottom wall of the piston 8| when the piston has moved substantially to the end of its discharge stroke. .The valve 81 is urged to closed position by a helical coil spring 88 which is positioned in a recess formed in the body boss 88. The valve 81 is reciprocal in a cylindrical cage 88 having outlet ports aligned with fuel ducts I88, I8I leading at an upward inclination to the wells I8, I8 respectively. The ducts I88,

I8I open into the wells I8, I8 substantially at the bottom ends thereof. The stem of valve 81 pro- Jects upward into the chamber 8| sufficiently so that the lower end of the valve will be limited by the wall of its recess before the piston 8| engages the top end of the valve cage 88 such as would close the power jet. The rod 82 is connected at its upper free end by a universal snap ball Joint to the end of a lever I82 extending through a slot I83 in the wall 8 between the chamber 8| and the float chamber 8. The lever I82 is rigidly fixed to a shaft I88 which extends horizontally through the float chamber 8 parallel with the throttle shaft 42 and has its ends Journaled in the float chamberwalls. One end of the shaft I88 projects externally of the float chamber adjacent the throttle shaft end 55 and has secured on its external end an operating lever I85 which is connected by a link I85 to an arm I81 of the throttle operating lever 58. The lever I85 may be provided with link receiving apertures I88 to receive the end of the link I88 at difl'erent radial distances from the shaft I88 in order to regulate the length of the stroke of the piston 8| to provide different pump discharge for summer or winter operation for the same extent of throttle movement.

The inlet member 8 carries and has formed integral therewith the float chamber cover I88 which is recessed on its underside to provide reinforcing ribs and a clearance space for the free end of the pump operating lever I82, see Fig. 4. The float chamber is vented to atmosphere from above the fuel level indicated by the line L-L by a passageway I I8 extending upward in the side wall of the member 8 and opening externally of the inlet member 8 through a horizontal port III. Each of the air inlet passageways 85 to, the nozzles 88, 8| is connected to the float chamber above the liquid level therein by a port I I2, see Figs. 5 and 6, so that any gas forming over the fuel in the float chamber will be drawn into the mixing chambers 8 and 5. The float chamber cover I88 is provided with an inlet fitting II8 for connection by a conduit (not shown) to the source of fuel. The bore or passageway II8 through the fitting H8 is provided with a vertically reciprocal upward seating inlet valve I I5 which is operated by a float arm II8 carrying a float member II1 which maintains the level LL. The arm or lever H8 is pivotally supported ona shaft 8 carried by lugs 'I I8 extending downward from the cover I88. The arm' II8 has an end portion I28 'engageable with the valve seat member I21 to limit the opening movement of the valve member I I5, thereby preventing disassembly of the pats and holding the inlet valve and its float together as a unit when the inlet member 3 and cover I are removed from the throttle body member 2. The members 2 and I are removably secured together by screws I22 which serve also to clamp a sealing gasket I28 between the members. The material of the gasket 02! and of the washers 25 and of the other gaskets and washers employed in the carburetor are preferably of synthetic rubber, such as Ameripol, so as to be unaffected by temperature or weather conditions.

The operation of this carburetor after its connection to the engine inlet manifold by bolting of the flange ll thereto, is as follows: When the float chamber inlet fitting H3 has been connected to the source of fuel supply fuel will fill the float chamber 9 to the level line L-L and will also fill the wells I8, I 9, the pump chamber 8i, and the idling conduits 41, 41' to this constant level line. On starting the engine, the choke valve in cold weather will, of course, have been moved to closed position by clockwise movement of the choke valve lever 61, the lever movement being sufllcient to take up the lost motion of the stop arm 1! in the slot 1| so that the choke valve 15 will be locked in closed position. This closing movement of the choke valve will cause the cam 68 to force its follower flange 58 toward the right of Fig. 2, thereby rotating the lever 51 in a clockwise direction so as to move the throttle valves 43, 44 toward open position sufllciently to maintain low speed operation of a cold engine. If the engine is now cranked, the sub-atmospheric pressure created in the passageways 4 and will draw fuel through the idling passageway jets 48, 48' for downflow through the passageways or conduits 5|, 5| and discharge of the fuel through the metered outlets 52, 52' into the passageways 4, 5 respectively. The fuel thus supplied to the passageways 4, 5 will be mixed with a minimum of air since the choke valve 16 is closed, thereby cutting ofl' the admission of air to the idle passageway bleeds 50,

50' and 54, 54 and to the primary air ducts 35 feeding the main nozzles 30, 3|. The air inlet passageway H0 to the float chamber remains open to atmosphere and therefore a minimum of air will be supplied to the primary air ducts 35 through the ports H2. Some fuel will also be drawn through the main nozzles 30, 3| thereby providing a rich fuel mixture for engine starting. As soon as the engine fires, the increased suction will open the auxiliary air inlet valve disc 18 to provide the necessary air to maintain cold engine operation. As the engine warms up, the operator will return the choke valve lever 61 counterclockwise, thereby permitting the spring 12 to come into play to permit automatic response of the air valve 16 to engine suction. When the engine has become thoroughly warmed up, the air inlet choke valve 16 will be returned to its full-open position which will permit the throttle valves to be moved to their full closed position, as shown, under the force of the spring 52. The necessary fuel mixture for engine idling operation will now be supplied through the metered ports 52, 52', the fuel being controlled at the jets 48, 48' and the necessary air being admitted through the bleeds 50, 50 and 54, 54'. As the throttle valves 43, 44 are moved toward open position, the quantity of air entering the bleeds 54, 54 will decrease, thereby providing a richer mixture from the ports 8 52, 52', in order to provide the desired mixture in the mixing chambers 4, 5 due to the increased air passing the throttle valves. At a further open position of the throttle valves, the flow through the bleeds 54, 54' will reverse and fuel will be discharged through these bleeds from the idle conduits 5|, 5| into the passageways 4 and 5 respectively. Continued opening of the throttle valves will increase the depression in the fuel nozzles 55, 3| until fuel is drawn through the nozzle lets 22 for mixture in the nozzles 'with air supplied through the primary air ducts I4, 35, this nozzle mixture being discharged into the mixing chambers 4 and 5. This rich fuel mixture from the main nozzles will impinge against the mid por. tions of the throttle valves 43, 44 and be broken up thereby for blending with the air entering through the inlets i. The fuel supply to the nozzles 20, 3| is compensated by the air vents 21, 25 such that when the throttle valves have been opened sufficiently to create a suction which will lift fuel from the level of the passageways 21, the air admitted by the bleeds 28 will pass through the wells l8, l9 and passageways 21 to form an emulsion of air and fuel which will be fed to the fuel nozzles. Still further opening movement of the throttle valves for ordinary road loads on the engine will increase the depression in the passageways 4 and 5 to an extent which will cause the fuel wells 18 and I9 to be emptied of fuel, the air from the bleeds 38 thereupon entering the lower cross passageways or air vents 28, thus further compensating for the increased suction on the main fuel jets 23, 24. If the throttle valves are moved to substantially wide open position, then the piston 9| will engage the power jet controllinS valve 91 and move it to open position so that additional fuel will be drawn from the float chamber through the pump chamber inlet check valve 52, the pump chamber 8i, and the open valve 51 for discharge through the passageways I00, llli into the wells l8, l8 respectively for supplementing the fuel supplied through the main jets 23, 24. This supplemental fuel supplied through the ducts I00, Illl will flow into the main fuel conduit through the lower air vents 28. The valve in the pump discharge conduit 86 prevents any downward air flow through the conduit 86 when the power jet valve 91 is open and also prevents fuel from by-passing the power jet and flowing by suction to the pump discharge nozzle 88 as might occur with the choke valve in closed position. When the throttle valves are quickly moved to open position for engine acceleration from part throttle operation or from a position for engine idling speed, then the piston M will be forced downward by the rod 92, thereby expelling fuel through the discharge duct sufficiently to open the, valve 90 and discharge the pump chamber fuel through the nozzle jets 89 into the air inlets 6 to supply the necessary enriched mixture in the passageways 4 and 5 for rapid engine acceleration. This supplemental fuel from the pump discharge will be continued after stoppage of throttle opening movement by reason of the expansible force of the spring 93 which was compressed by the quick downward movement of the piston rod 92, thereby giving a desirable pro- 76 described, in addition to the pump discharge.

What is claimed and is desired to be secured by Letters Patent of the United States is:

1. In a carburetor, a casing having a pmsageway therethrough, an unbalanced choke valve in said passageway and having an operating shaft extending from said casing, a disc rigid on the end of said shaft external of said casing, an arm projecting from said disc toward said casing, a valve operating lever interposed between said disc and said casing and journaled on said shaft, a coil spring interposed between said disc and said lever and interconnecting said arm and said lever and acting to move said valve in a closing direction relative to saidlever, said lever having a slot receiving said arm and providing an abutment on said lever and engageable by said arm to limit closing rotation of said valve relative to said lever by said spring, said slot providing a second abutment on said lever engageable by said arm and determining th extent of valve opening movement by air pressure against the force of said spring, said second abutment being operable through said arm to hold said valve closed against air pressure.

2. In a downdraft carburetor, a casing having a mixing passage with an air inlet, a throttle valve in said passage, a fuel conduit having an outlet discharging into said passage on the inlet side of said valve, said conduit having a portion of its length bridging said passage on the outlet side of said valve so that said conduit portion is positioned across the path of the discharging and expanding fuel mixture to be cooled thereby.

3. In a downdraft craburetor, a casing having a mixing passage with an air inlet, a throttle valve in said passage, a fuel nozzle discharging into said passage anterior to said throttle valve, 9. fuel well extending upward at one side of said passage and discharging into said nozzle, an idling conduit extending upward at the other side of said passage, a fuel reservoir feeding said well, and a fuel supply conduit connecting said well to said idling conduit below the reservoir liquid level, said supply conduit extending across said mixing passage posterior to said throttle valve so that fuel in said supply conduit will be cooled by the expansion of the air and fuel mixture after passing said throttle valve and discharging through said passage.

4. A carburetor comprising a casing having a pair of vertical mixing chamber passageways therethrough, each passageway having an air inlet and a mixture outlet, said casing having a pump chamber and a fuel reservoir, a fuel inlet controlling float member in said reservoir, main fuel nozzles discharging one into each of said passageways, a conduit leading from said pump chamber and having a. plurality of outlets one into each of said passageways on the air inlet side of said nozzles, a vertical wall separating said passageways from said reservoir, said pump a hollow clamping flange forming around and with said outlet portion a downwardly open air flow channel, a fuel nozzle discharging downward into said passageway, a fuel reservoir integral with said body member, a hollow boss extending downward from said body member into said channel, said body member having a vertical fuel duct extending upward from said boss and connecting into said nozzle, a hollow plug positioned in said channel and sealed in said boss an-dhavlng a horizontal fuel jet communicating through said plug with said duct, said body member having a fuel duct of uniform cross-section leading from said reservoir downward to said jet thereby to eliminate trapping of gas bubbles, and said flange having air flow openings for convection new of cooling air through said channel around said boss and plug.

6. A carburetor comprising a casing having a passageway therethrough providing a, mixing chamber having an air inlet, a throttle valve in said chamber, a fuel nozzle discharging into said chamber, a shaft supporting said valve and hav-- ing an end portion projecting from said casing, an air pressure moveable air valve in said passageway and controlling said air inlet, a shaft supporting said air valve and having an end portion projecting from said casing, a lever journaled on said air valveshaft so that said air valve can rotate relative to said lever, said lever having a cam operable to move said throttle valve toward open position upon closing movement of said air valve, said lever having spaced abutments, an arm fixed on said air valve shaft and extending between said abutments, a spring urging said arm in a valve closing direction relative to said lever and against one of said abutments so that said air valve is moveable with said lever, the other of said abutments being spaced from and engageable by said arm to limit opening movement of said air valve by air pressure against the force of said spring, said spring having one end anchored to said arm and having its other end anchored to said air valve lever, a lever carried by said throttle valve shaft and having a follower portion engaging said cam, means interconnecting said last-named lever and said throttle shaft so that said throttle valve is opened by closing movement of said air valve, and a spring urging said follower portion against said cam and said throttle valve toward closed position.

7. In a downdraft carburetor, a casing having a mixing chamber passageway therethrough and having a fuel reservoir, a vertical wall separating said passageway and said chamber; a. throttle valve in said passageway and having an operating shaft, said wall having a transverse inclined bore therethrough directed downward toward said shaft, a nozzle member in the passageway chamber being in said wall and between said passageways and said reservoir, said wall having a vertical slot above the reservoir liquid level and connecting the interior of the pump chamber to said reservoir, an operating shaft in said reservoir and journaled in the side walls of said reservoir and positioned between said slot and said float member, a piston in said pump chamber, a lever rigid on said shaft and extending through said slot and interconnecting said shaft and said piston, and means to rotate said shaft.

5. In a downdraft carburetor, a throttle'body member having a vertical passageway terminating at its lower end in a tubular outlet portion,

end of said bore, a plug member closing the reservoirend of said bore and spaced from said nozzle member for admission of air thereto, said wall having a vertical bore which opens from the bottom of said casing into said inclined bore, said nozzle member having a fuel port communicating with said vertical bore, said vertical bore bein enlarged to provide a socket portion adjacent said inclined bore and being still further enlarged to provide a well, a tubular plug having one end fitting said socket portion and having a flange at its other end fitting the bottom portion of said well, said other plug end having a socket, a fuel jet member screw-threaded into the bottom end of said vertical bore and having a projecting portion fitting said plug socket, a gasket between said plug flange and said jet member, said cas- 1213 having a, port for fuel flow from said reservoir to said jet member, said plug having crossports for air flow to said nozzle member, and means to supply air to said well around said tubular plug.

' WALTER H. WEBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 12 Name 0 Due Beard Aug. 22, 1933 Kenneweg Apr. 3, 1934 Holley May 18, 1937 Goodman Oct. 12, 1937 Hunt July 26, 1938 Thieuiin Apr. 25, 1939 Winkle: June 27, 1939 Nieman Nov. 21, 1939 Ensign Jan. 9, 1940 Cofley July 30, 1940 Mock et a] Aug. 27, 1940 Emerson June 3, 1941 Winfield June 24, 1941 Wir-th et a1 Mar. 28, 1944 Boylan Aug. 8, 1944 St. Clair Jan. 15, 1948 

